System and method for imaging and locating punctures under prostatic echography

ABSTRACT

The present disclosure relates to a prostatic imaging system including steps of recording and processing images acquired by the ultrasonographic head of a rectal probe equipped with an active puncture guide, characterised in that it includes steps of processing at least a part of the images acquired by the probe for calculating transformations to a “reference image” repository relative to the initial position of the prostate, at least a part of the images acquired during the successive punctures including the location of the various positions of the needle being recorded with a view to visualising representations thereof on a single image including at least a part of the prostate. The present disclosure also relates to a system for the prostatic imaging implementing said prostatic imaging method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Entry of International ApplicationNo. PCT/FR2008/001306, filed on Sep. 18, 2008, which claims priority toFrench application Ser. No. 07/06544, filed on Sep. 18, 2007, both ofwhich are incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to the field of the methods and equipmentintended for the computer-aided diagnosis and therapeutic treatmentapplied to prostate pathologies and more particularly cancer. It moreprecisely relates to a method and a system for locating in vivobiological samplings done using a transrectal ultrasonographic probe.

BACKGROUND

Prostate punctures, more particularly needle-biopsies, are carried outin a standard way through a transrectal ultrasonography. Theultrasonographic probe includes a puncture guide mechanically positionedso that the path of the puncture needle is in a/the sagittal acquisitionplane of the probe. The positioning of the needle with respect to theorgan is made through a visual guiding more particularly using theultrasonographic pictures of said acquisition plane. For a 3D probe,“sagittal plane” will mean the probe “field of view” and, if need be,the mid-plane of the field of view.

In the case of the needle-biopsy, to carry out analyses, thepractitioner will comply with a pre-defined puncture scheme of at leastsix punctures, with twelve being the standard. From this scheme, he/shemust distribute the sampling in a homogenous way in the prostate areaopposite the rectal probe head to optimise the chances of detecting apossible tumoral focus. The main difficulty consists in making acoherent distribution of the puncture points which can be optimum asregards the first diagnostic results on an organ which is not directlyvisible to an operator, which is not immobilized and which is deformedduring the operation. The handling of the probe head thus requires bothgreat skills and a strong experience to guarantee that the actual pointof the sampling will match that on the scheduled puncture scheme.

This difficulty in guiding the puncture head to a theoretical target afortiori implies the practitioner failing to know the exact position ofthe sampling carried out. This lack of information may lead to anincorrect diagnosis which is useless and also to repeated biopsies or toa non-focussed or at least a non-optimal therapy. The information on theintra-prostatic location of the puncture head is the key of a system forefficiently and globally treating prostatic pathologies and moreparticularly cancer.

International Application WO2005/110255

The international application WO2005/110255 provides for a solution forthe targeting and the biopsy of tissues for medical purposes, and moreparticularly a targeted biopsy system, which enables the planning of thetissue to be sampled, the targeting of specific areas of the tissues,with reference to the plane, the capture of the tissue sample and therecording the source location of the tissue sample. The system is moreparticularly used for collecting samples of tissues from the prostategland. It includes a flexible biopsy needle, a directional guide forsaid biopsy needle, imaging means, a biopsy scheme and recording means.

Drawbacks of Such Solution WO2005/110255

The problem entailed in this solution is that the identification of theprostate on the image is purely mechanical. Therefore, the image of theneedle with respect to the prostate is calculated using a succession ofreferences:

the “operation room” reference which makes it possible to determine theposition of the probe using the support;

the “patient's body” reference which is likely to move with respect tothe “operation room” reference;

the “organ” reference which is liable to move and be deformed withrespect to the “patient's body” reference;

the “probe” reference which is theoretically stationary with respect tothe “operation room” reference, but the mechanical connections are notabsolutely rigid and thus lead to a possible shifting.

The image of the probe with respect to the prostate is thus calculatedwith an accumulation, or rather a multiplication of uncertainties andleads to localising the probe with respect to the prostate with severalmillimetres' inaccuracy. Therefore, the position of the sample withrespect to the gland cannot be recorded nor used. Consequences aresignificant: the tumoral area is known only within several millimetres'accuracy, which entails treatments on needlessly large areas. Underthese conditions, a therapeutic treatment, for example by localirradiation, cannot be focused on the tumoral area.

International Application WO2004/019799

From the international application WO2004/019799 is also known, in theprior art, a method to determine the position of a biopsy needle withina target volume, said target volume being defined as a space inside apatient. The method consists in:

generating several images of the target volume,

spatially recording the images for generating a three-dimensionalrepresentation of the target volume from the recorded images,

determining the location of the biopsy needle in the three-dimensionalrepresentation of the target volume, and

correlating the determined biopsy needle location with the spatiallyrecorded images.

The graphic of the target volume includes a graphic representation ofthe determined location of the biopsy needle. This document alsodescribes a locating technique wherein a camera tracking a referencetarget is fixed to an ultrasonographic probe, which enables an accuratelocalisation of the probe in a coordinate system. However, in thesolution described in this document, the space inside the patient is notprecisely defined: it can be interpreted as an assembly of tissuesbelonging to a patient or as a volume, the position and orientation ofwhich are defined with respect to a coordinate system outside thepatient.

In the first case, the system determines the position of the needle withrespect to the patient's anatomy, whereas in the second case, the systemdetermines the position of the needle with respect to a reference systemoutside the patient. In the second case, it is essential that thepatient and the targeted organ do not move and are not deformed duringthe operation, or the position of the needle calculated in the targetedvolume will not match the position of the needle with respect to thepatient's anatomy.

It is clear, with the encapsulating volume and the reference systemx-y-z as shown in FIG. 1 of such international application, as well aswith the description of the locating methods (D1, p. 13 1.24-p. 14 1.35)that the system provided is in the second case. Several methods areprovided, which all aim at localising the position of theultrasonographic image with respect to an external and thus non-anatomicreference. The first method (D1, p. 13, 1.24-37) is stereotactic andlocalises the images with respect to the camera reference system. Thesecond method is acoustic (D1, p. 13, 1.38-p. 14) and localises theimages with respect to the pinger reference.

The third method provided (D1, p. 14, 1.5-1.35) is mechanical and thusconsists in fixing the path of the needle using a guide with respect tothe probe, and in immobilizing the prostate at the same time with a pawlto reduce the mobility thereof, and in determining the position of theprobe (and thus of the needle) with a mechanical system (e.g. an encodedarticulated arm), the identification for such system. The pawl makes itpossible to reduce the movement of the prostate resulting from themovement of the probe but it cannot make up for the patient's motions(as he or she is locally anesthetised). As a summary, the systemprovided in the prior art document is capable of determining the needlewith respect to an identification system inside the patient and thusrequires that the targeted tissues do not move during the operation toobtain clinically satisfactory results.

Drawbacks of Such Solution WO2004/019799 and Solution Provided by theInvention

The claimed invention is based on a method for localising the needlewith respect to an anatomic identification system, the latter beingdefined by a 3D reference image containing the targeted anatomy, i.e.the prostate. The matching of imaged tissues in the tracking images andreference images makes it possible to be independent of externallocalising systems such as those described in the internationalapplication WO2004/019799. The invention thus makes it possible tomanage the “jumps” of patients which are well-known to the practitionersand which result from the pains caused upon the triggering of the biopsygun, thanks to the utilisation of a purely anatomic identificationsystem.

Patients jump approximately in 10 to 20% of transrectal prostatebiopsies operations. The invention also makes it possible to avoidproblems relative to the motions of the prostate more particularlyresulting from the motions of the endorectal probe. The documentWO2004/019799 does not provide the exploitation of one of the acquiredimages in order to determine the “reference image” relating to theinitial position of the prostate.

The method provided in this document also aims at the same goal, but itimplements a totally different means: it makes it possible to equip theexternal part of the probe with a camera which records the image of apattern outside the patient and used for resetting the position of theprobe. The part of the probe which remains outside the patient's body isprovided with a camera which must be oriented to a stationary patternfor example glued on a wall of the operating block or the equipmentsupporting the patient.

The drawbacks of such solution are multiple:

it imparts constraints which are an obstacle to ergonomics and operationof the probe,

it provides an external reference in the operating block and notdirectly connected with the observation area, i.e. the prostate itself,

it does not make it possible to prevent the interferences resulting fromthe patient's untimely motions.

it implies the passage through a succession of references degrading theprecision of the transformations:

“Operating block/patient's body” transformation,

“Operation room/prostate” transformation.

This document thus does not disclose the claimed characteristics anddoes not suggest these obviously for the persons skilled in the art.

International Application WO2006/089426

This document relates to a system and a method for performing a biopsyof a target volume and a computer device for planning the same. Anultrasonic transducer captures ultrasound volume data from the targetvolume. A three-dimensional recording module records the ultrasoundvolume data with supplementary volume data relative to the targetvolume. A biopsy planning module processes the ultrasound volume dataand a supplementary volume data in combination in order to develop abiopsy plane for the target volume. A biopsy needle biopsies the targetvolume in accordance with the biopsy plane. A solution consisting ininjecting a pre-operational “additional” image, on a per-operational“probing” image used for guiding a practitioner's gestures (§46 p. 13).The approach claimed in the present invention is different in that itaims at localising the organ during the punctures, with respect to areference position.

The system described in the document WO2006/089426 also uses thelocalising of the images in a non-anatomic and external reference systemto determine the position of the needle in the reference volume (FIG. 4,108 and p. 22, 1.8-121 and §64 p. 16 with the support and MCM). The“three-dimensional” ultrasonography obtained with this method (FIG. 7,FIG. 8, FIG. 4 132, §139 p. 11) is different from the actual 3Dultrasonography on which an advantageous variant of the present claimedinvention is based, as regards the quantity of available data, speed,collision and fineness of the 3D anatomic reconstruction. The systemprovided in the document WO2006/089426 is thus exposed to the samedefects as those identified for the system disclosed in the documentWO2004/019799. More particularly, the movements of the organ and, afortiori, of the patient disturb the whole guiding method.

SUMMARY

The aim of the invention is thus to remedy such drawbacks whileproviding a solution making it possible to improve the precision of thebiological samplings and the localising of corresponding test specimens.In addition, the solution brought by the present invention makes itpossible:

prior to the operation, to define a puncture planning which can betransferred to the per-operational time by resetting the data;

at the per-operational level, to guide the needle and visualise thespatial distribution of the already done punctures;

after the operation to visualise the spatial distribution of thepunctures done; in the case of the biopsy, this is the distribution ofthe samples and the tumoral tissue identified during ananatomopathological analysis to make a diagnosis and help the planningof a focused treatment.

The guiding of the per-operational needle and the precise identificationof the puncture sites, made possible by the invention, makes a focusedpost-operational treatment possible. For this purpose, the invention inits broadest sense also relates to a prostatic imaging method includingsteps of recording and processing images acquired by theultrasonographic head of a rectal probe provided with an active punctureguide, characterised in that it includes steps of processing at least apart of the images acquired by the probe to calculate thetransformations to a “reference image” repository relative to theinitial position of the prostate, at least a part of the images acquiredduring the successive punctures including the localising of the variouspositions of the needle being recorded with a view to visualising therepresentations thereof on a single picture including at least a part ofthe prostate.

In a particular embodiment, the position of the sampling needle isvisualised in the “reference image” repository or the “tracking image”repository after puncture, superimposed on an image of at least a partof the prostate showing the various positions of the prior samplings. Inanother particular embodiment, the performed or theoretical position ofthe sampling needle is visualised in real time in the “reference image”repository or “tracking image” repository, being superimposed on animage of at least a part of the prostate showing the various positionsof the prior samplings. In another particular embodiment, thedistribution of the tumoral tissue is visualised in the “referenceimage” repository after merging the distribution of marked punctureswith the results from the anatomopathologic analysis. Preferably, theinvention includes the steps of recalculating a new prostatic markedimage at each sampling.

According to an advantageous variant, the refreshing frequency of theimages acquired by the ultrasonographic probe is of at least 3 picturesper second. According to an advantageous alternative, a flow of imagesis acquired, the periodicity of which depends on the refreshingfrequency of ultrasonographic images, the speed of transfer to thecomputer and the processing speed of received images. According to afirst exemplary implementation, the ultrasonographic probe gives athree-dimensional imaging. According to a second exemplaryimplementation, the ultrasonographic probe gives a “2.5 dimensional”type imaging (2D images localised in space). Preferably, the imagingmethod according to the invention includes a step of chronologicalmarking with a serial number implementing univocal labelling means foreach sampling area.

According to a first exemplary embodiment, the univocal labelling meansare manually generated when the needle is in position. According to asecond exemplary embodiment, the univocal labelling means are generatedby triggering the manual data acquisition or automatic data acquisitionthrough the capture of a sound, light, magnetic or tactile signal at thevery moment of a biopsy sampling.

In a particular embodiment, the step of processing the acquired imagesfurther implements a kinematic model derived from the anatomicconstraints which are specific to a transrectal puncture of the prostatethus making it possible to identify probable positions of the probeduring the operation. In a particular embodiment, the step of processingthe acquired images further implements a process of pre-calculating theprobable positions of the probe during the biopsy and imagescorresponding to the pre-calculated positions of the probe from thereference image. Advantageously, the step of processing the acquiredimages further implements an image resetting algorithm based on thelocal optimisation of a measure of the similarity.

The invention also relates to a prostatic imaging system including arectal probe and a calculator, the probe including an ultrasonographichead for taking an image of the punctured area done with a needleactuated by the operator or automatically, with the calculator includingmeans for recording and processing of images acquired by saidultrasonographic head, characterised in that the computer includes meansfor the recording and processing of the images acquired by the probe tocalculate transformations to a “reference image” repository relative tothe initial position of the prostate, at least a part of the imagesacquired during the successive punctures including the localising of thevarious positions of the needle being recorded with a view tovisualising the representations thereof on a single image including atleast a part of the prostate. Preferably, the system further includes areceptacle for the collection of tissue samples with an identifiercorrelated with the marking of the corresponding sampling area of thesingle image of the marked prostate. Advantageously, the systemintegrates a system for creating labels to be applied onto thereceptacle bearing the above-mentioned single identifiers. The editingsystem can be composed by a thermal printing machine or an inkjetprinting machine, adding a barcode or a matrix code.

According to a first exemplary embodiment, the rectal probe is amanually operated probe without any robotised positioning. According toa second embodiment, the rectal probe is a manually operated probeactuated by an optical or magnetic locator. According to a thirdexemplary embodiment, the rectal probe is a robotised-positioning probe.The invention also relates to a computer medium including the recordingof a calculator control programme, for the implementation of theabove-mentioned method.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood when reading the followingdescription relating to a non-limitative exemplary embodiment, wherein:

FIG. 1 is a diagram of the prostatic imaging system;

FIG. 2 is a diagram of the management procedure of the prostatebiopsies;

FIG. 3 is a diagram of the procedure of creation of a biopsy planning;

FIG. 4 is a diagram of a variant of biopsies acquisition method, alsocalled “consultation during the operation”;

FIG. 5 is a diagram of a variant of biopsies acquisition method, alsocalled “guiding during the operation”;

FIG. 6 is a diagram of a variant of biopsies acquisition method, alsocalled “post-operational consultation”;

FIG. 7 is a diagram of the method for preparing the estimation oftransformations to the reference image;

FIG. 8A shows the kinematic model of the probe with respect to theprostate in a first position of said probe;

FIG. 8B illustrates the kinematic model of the probe with respect to theprostate in a second position of said probe;

FIG. 8C illustrates the kinematic model of the probe with respect to theprostate in a third position of said probe; and

FIG. 9 is a diagram of the method for estimating the tracking image tothe reference image.

DETAILED DESCRIPTION

The present exemplary embodiment relates to a system implementing amedical imaging method enabling the acquisition and analysis of 3Dultrasonographic images with a view to localising samples or needleswith respect to the prostate. Images resetting algorithm for thestatistical analysis of similarities enables the matching of all theacquisitions in the same repository relative to the organ.

Prior to the operation, a graphic interface makes it possible for theclinician to plan a diagram of punctures on a first ultrasonographicacquisition. Several options are offered:

a manual planning without any constraint;

an equally distributed automatic planning for a defined number ofsamples with possible manual corrections, afterwards;

a differential planning, i.e. the visualisation of the previouspunctures superimposed on the actual acquisition in case of repeatedoperations;

the transfer of a planning carried out on an external imaging forexample of the MRI type.

The system can be used and the method implemented according to threeembodiments:

prior to the operation, the system can, after each puncture, show in aview which is annexed to the real time ultrasonography, the position ofthe samplings carried out so far during the operation. For eachpuncture, the 3D ultrasonographic acquisition can be either manual orautomatic through a, for example sound detector. This embodiment will becalled “consultation during the operation”.

during the operation, if the computer equipment enables it, the systemcan represent in real time on the ultrasonographic guiding image or on amodel, the actual position of the puncture guide with respect to theorgan. This mode of utilisation can be added to the preceding one. Thereal time tracking coherent with the position of the organ is providedby the resetting algorithm of the present invention; however, it canrest on location information supplied by an external (optical, magnetic,etc.) locator. This embodiment will be called “guiding during theoperation”.

after the operation, the system offers the clinician a 3D visualisationof the punctures carried out with, if need be, a quantitative comparisonwith a prior operation, for quality purposes. The post-operationinformation on the distribution of tissue samples makes it possible,together with the results of the anatomopathological analysis, toprecisely show the tumoral areas with respect to the prostatic volume.Such information which is useful for the diagnosis can be shared andtransmitted to the therapist, which will have the possibility offocusing the treatment.

The system is composed of various elements as illustrated in FIG. 1. Arectal probe 1 makes it possible to position precisely a core drillingneedle 12. As a matter of fact, a core drilling needle 12 is integralwith the rectal probe 1. It is liable to take two positions: a firstposition where said needle 12 is located inside a guide integral withsaid rectal probe 1 when no core drilling is in progress and a secondposition where said needle 12 is located outside said rectal probe 1when the coring is in progress so as to sample some biological tissue.

An ultrasonographic head 11 is positioned at the end of the rectal probeso that the position of said rectal probe with respect to the prostatenot visible during the handling of said rectal probe 1 can be observedon a monitor 3 via a system for the acquisition and analysis of images2. The probe can also be composed of a side or oblique sight 3D probe.Said ultrasonographic head 11 is a 3D ultrasonographic head. In aparticular embodiment, said ultrasonographic head is a “2.5-dimensional”type imaging ultrasonographic head. Said “2.5-dimensional” type imagingis defined as an image system implementing spatially localised 2Dimages. In an advantageous variant, the ultrasonographic head 11 isprovided with an optical or magnetic marker capable of communicatingwith an optical or magnetic locator so as to make the tracking in realtime easier.

A monitor 3 makes it possible to visualise the flow of images acquiredby the ultrasonographic head 11. The visualisation of the flow isoperated at the refreshing rate of images acquisition and analysissystem 2. Said monitor 3, or in a particular variant, a second monitor,makes it possible to simultaneously visualise the “reference image”repository or the “tracking image” repository which may include theplanned puncture paths, the presently targeted path and the previouspaths. The refreshing rate of said visualisation of the “referenceimage” repository or the “tracking image” repository depends on theperformances of the image acquisition and analysis system 2. Saidvisualisation makes it possible for the clinician to observe theposition of the rectal probe 1 with respect to the organ and/or toobserve the sampling area actually punctured after the triggering of acore drilling.

A control table 4 makes it possible for the clinician to carry out thevarious adjustments required for the correct execution of a biopsyscheme. More particularly, it is possible to control the establishmentof a biopsy planning to choose the way the sampling targets areidentified systematically through a differential calculation, from anexternal image or manually, and to choose the fineness of thecalculations upon the processing of the images. Advantageously, saidmonitor 3 is a touch screen displaying virtual graphic objectscorresponding to at least a part of said control table 4 or any othercontrol table.

A gun 13 makes it possible to perform core drilling. As a matter offact, it is provided with a (not visible) actuator and mechanicallyconnected to the core drilling needle 12 so that the triggering of theactuator by the clinician causes the request for the acquisition of animage by the ultrasonographic head 11 during the next period of theimaging method. In an advantageous variant, the ultrasonographic head 11and the gun 13 are in a triggering mode without any contact for theautomatic acquisition of ultrasonographic images upon the core drilling.A (non-visible) receptacle is provided for the collection of the sampletissues, with an identifier correlated with the marking of thecorresponding sampling area on the single image of the marked prostate.

A sample marking device or labelling device is used so that eachsampling area can be identified univocally. The labelling meansimplemented are generated in a chronological order of the biopsiesperformed, whatever said chronological order selected by the clinician,without the cohesion of the results being affected. As a matter of fact,the system is not sensitive to a discrepancy between the spatialdistribution and the chronological order of biopsies, since with eachsampling is associated an image which cannot be confused with the imageassociated with another sampling.

In a particular embodiment, the labelling means are manually generatedwhen the core drilling needle is positioned. In another particularembodiment, the univocal labelling means are generated by an automatictriggering of data acquisition for the capture of the sound, light,magnetic or tactile signal at the very moment of the biopsy.

The image acquisition and analysis system 2 is a system capable ofcommunicating through communication channels 21, 22, 23, in additionwith the ultrasonographic head 11 for the control of image acquisitions,with the control table 4 for the adjustment by the clinician, and withthe monitor 3 for the visualisation of the processed images. Said imagesacquisition and analysis system 2 includes a (not visible) computermedium making it possible on the one hand to record the acquired imagesand on the other hand to record beforehand the control programme of a(not visible) calculator for implementing methods for processingacquired and recorded images and methods for estimating core drillingneedle position with respect to a biopsy planning. Said imagesacquisition and analysis system 2 further comprises a (not visible)ultrasonographic system enabling the acquisition of images and thetransfer thereof to the above-mentioned computer medium.

The method for processing acquired and registered images furtherimplements an image resetting algorithm based on the optimisation of asimilarity measurement, from the global optimisation, from positionssupplied by a kinematic model and followed by one or several localoptimisations. A pre-calculation step of the positions of the model andcorresponding images makes it possible to decisively accelerate theglobal optimisation.

The procedure of management of biopsies is illustrated in FIG. 2. Suchprocedure mainly has two steps:

a preliminary sequence including the acquisition of reference image 101,the preparation of the estimation of the transformation to the referenceimage step 102 and possibly the preparation of the sampling planningstep 103; and

a sequence of sampling collection.

Such steps are successive with the patient remaining on the operationtable and the various sequences being performed during the sameoperation without the patient's significant motion for a single biopsysequence, the duration of which is of a few dozens of minutes. The timebetween the acquisition of the reference image and the performance ofsamplings can be from a few seconds to a few minutes.

The preliminary sequence starts with the acquisition of the referenceimage of the current biopsy series 101. Said reference image is definedas the entire image of the prostate, acquired by the image acquisitionand analysis system 2 during the preliminary time, prior to the handlingof the system by the clinician.

Such reference image acquisitions step consists in acquiring one orseveral adjacent ultrasonographic images for example three images in theexample described, with the ultrasonographic probe, the practitionermodifying the orientation of the probe head between each acquisition toobtain three distinct images of the prostate. Such three images areobtained by the application of a processing on these three digitalimages so as to recalculate the single image, also called “referenceimage” corresponding to a three-dimensional view of the whole of theprostate. Each one of the initial images generally covers only a part ofthe prostate and the combination of the images taken along slightlydifferent angles makes it possible to reconstruct an image of the wholeprostate as it is, the positioning and the configuration of the prostateand of the patient corresponding to the acquisition sequencing comingvery shortly prior to the sampling sequencing. This “reference image” isacquired with the same equipment and under the same conditions as theimages which will then be required during the sampling steps.

Such reference image is used for preparing the successive positions ofthe rectal probe 1 based on the biopsy scheme. From said referenceimage, the computer makes a step of preparing the estimation of thetransformation to the reference image 102. Such step of pre-calculationmakes it possible to pre-estimate the probable positions of the probeand the images corresponding to this position. It requires several stepswhich will be described hereinunder and illustrated in FIG. 7. Theclinician also can choose between the drawing up of a planning 103 ornot. The planning makes it possible to position a distribution card withone or several series of biopsies thus facilitating his or her workduring the acquisition of biopsies 104. The step of drawing suchplanning will be described hereinafter and illustrated in FIG. 3. As theultrasonographic probe is guided 1, the images of the various samplingareas corresponding to the possible planning 103 for the biopsy areacquired and stored on the computer medium of the images acquisition andanalysis system 2. The result of the acquisition of biopsies 104 havingbeen obtained, the practitioner can carry out a post-operationalconsultation of the distribution of biopsies 108, in combination withthe integration of an anatomopathological analysis 109 so as toestablish whether a treatment is recommended or if a new series ofadditional biopsies is required or if the patient has no pathology asregards the prostate.

The procedure for drawing up the planning 103 for the biopsy isillustrated in FIG. 3. If maps showing the distribution of one orseveral series of previous biopsies for the same patient are available,the computer makes a projection of the previous sites of biopsies in thereference image of the current series 111. The practitioner can haveaccess to the visualisation of targets and previous sites of biopsy 112through the visualisation screen 3. The clinician has the possibility ofchoosing then the drawing of the biopsy planning according to fourdistinct modes. If the clinician requests a differential preparation ofoptimal sampling targets and if projections of biopsy sites beforehandare available, the calculator calculates the optimum targets in thenon-biopsied sites 113. If the clinician requests the positioning ofsystematic targets at N samples, with N being a parameter definedbeforehand by said clinician, the calculator selects the systematicprotocol 114, then the anatomic projection of the targets into thereference image of the current series 115, the manual adjustment 116being then manually carried out by the clinician. If the clinicianrequests the definition of targets from an image having a modality whichis not an ultrasonographic external image obtained for example by a MRI,the calculator defines the target in the external image 117 and then itprojects external targets into the reference image of the current series118 by a multi-modal matching. Finally, if the clinician requests themanual definition of targets, he/she will carry out said manualdefinition of targets in the reference image 119. Finally, if theclinician considers that the planning is not completed, the followingsteps will thus consist again in visualising targets and biopsy sitesbeforehand 112 with, again the same possible selection available to theclinician. If not so, the step of drawing up the planning 103 of biopsyis completed.

The step of acquisition of biopsies 104 can be carried out in threevariants, as a function of the ultrasonographic system and the computerdevice used. The first variant also called “guiding during theoperation” 105 requires a real time flow of 3D ultrasonographic imagesmaking it possible to identify and visualise at any time the position ofthe current puncture path. Such variant makes it possible to guide thisprobe insofar as the image is acquired and refreshed at a rate of morethan 3 images per second. The guiding of the probe by the clinician isthus facilitated, and thus the identification in real time of the nextpuncture site. On the contrary, as the acquisition of the image is notcarried out at the precise moment when a biopsy is triggered, theacquired and recorded image not exactly corresponds to the sampling madeat the moment of the sampling. Advantageously, a sound, light, magneticor tactile system for detecting the biopsy can help synchronising thetracking image with the biopsy. In the second variant also called the“consultation during the operation” 106, the acquisition and transfer ofa 3D image occurs only after the acquisition of biopsy thus eliminatingthe required real time flow but supplying an immediate per-operationalreturn on the puncture path. If the computer system makes it possible,said first variant and said second variant can be added. Finally, thethird variant also called “post-operational consultation” 107 simplyuses the recording of 3D images in per-operational time and onlyestimates the puncture paths after the operation.

In the first variant also called the “guiding during the operation” 105and illustrated by FIG. 4, the acquisition of the tracking image 122 isperformed independently of a gun. Such tracking image is defined as theimage acquired by the acquisition and analysis system for images duringthe handling of the system by the clinician. The system can show in realtime, on the guiding ultrasonographic image or on a model, the currentposition of the puncture guide with respect to the organ. The real timetracking in cohesion with the position of the organ is provided by theresetting algorithm of the present invention; it can however rest onlocation information supplied by an optical, magnetic, mechanical orrobotic external locator. If all the biopsies are carried out, suchprocedure is completed. If not all the biopsies have been completed, amethod composed of a succession of the steps 121 to 125 is carried outso as to actualise the data of the device and to acquire a new image atthe rate of at least 3 images per second. The first step consists in theupdating of the visual rendering of the reference image 121 includingthe biopsies completed paths, planned biopsy paths and the estimation ofthe sampling path. It makes it possible for the clinician to observe onthe visualisation screen 3 the reference image with the informationrequired for the guiding of the rectal probe 1. The method thenimplements a succession of the steps 122 to 125, so as to carry out theacquisition and processing of the images. This succession of stepsincludes the acquisition of the tracking image 122 by the imaging device2. The calculator then carries out an estimation of the sampling path inthe first image of the list 123. Then the method implements theestimation of the transformation of the tracking image to the referenceimage 124. This estimation implements the calculation algorithm and willbe better illustrated in FIG. 9. The calculator finally projects theestimated path in the reference image 125. If during such succession ofsteps no sampling is carried out with the gun and if all the biopsieshave not been completed, the procedure repeats the steps 212 to 125. If,on the contrary, a sampling has been carried out with the gun during thetime between two refreshing operations, then the imaging device 2 willadd the estimated path to the completed biopsy path 126. If, whenconsidering this added path all the biopsies have been completed, theprocedure is completed. If not so, the steps 121 to 125 are repeated.

In the second variant also called the “consultation during theoperation” 106 and illustrated in FIG. 5, the acquisition of thetracking image 122 is triggered by a gun. The system can, after eachpuncture, show on an appended view the ultrasonographic image in realtime, with the position of the samples carried out so far during theoperation. If all biopsies are completed, this procedure is completed.If all biopsies have not been carried out, the first step consists inthe updating of the visual rendering of the reference image 127. Thisstep includes the completed biopsy path and the planned biopsy path. Aslong as a sampling is not triggered, the system carries out only step121. When a sampling is triggered, the method implements a succession ofthe steps 122 to 126, so that the acquisition and the recording of theimage is carried out. Such steps 122 to 126 are identical to the steps122 to 126 described in the first variant also called “guiding duringthe operation” (FIG. 4). If, considering the new added path, allbiopsies have been complied, the procedure is over. If not so, the step121 is repeated in a cycle, so long as a new sampling is not triggered.It should be noted that in such second variant, the user can control atracking image prior to the biopsy so as to visualise a reliableestimation of the current place aimed at by the gun.

In the third variant also called “consultation after the operation” 107and illustrated in FIG. 6, the processing is carried out after theoperation. So long as all biopsies are not acquired, at each samplingcarried out with the gun the method implements the step of acquisitionof the tracking image 122, then a step of storing said acquired trackingimage 128. If, on the contrary, all the biopsies have been acquired, andso long as there is still a stored image to be processed, the steps 123,124, 125 and 126 such as defined for the procedure also called the“guiding during the operation” are implemented so as to process thestored images.

The method of preparation of the estimation of the transformation to thereference image 102, implemented prior to the possible drawing up of aplanning 103, is illustrated in FIG. 7. The first step consists indetermining a volume surrounding the prostate 131. The position of theprobe is then calibrated with respect to the reference image 132. Thekinematic model is initialised 133. Then the calculator pre-calculatesprobable positions for the probe during the biopsy 134 then thepre-calculation from the reference image of the images corresponding tothe positions of the pre-calculated positions of the probe 135. Moreexactly, for each position supplied by the kinematic model, thereference image is re-sampled so that the resulting image corresponds tothe reference image if it had been acquired in this position, within thelimit of the available information in the reference image and withoutconsidering any deformation. The images are kept in the random accessmemory so as to enable a quick access subsequently. As a matter of fact,the calculated images and the corresponding transformation are stored ina list 136. This list of pre-calculated elements is used during theoperation by the method of estimation of the transformation of thetracking image to the reference image 125, as illustrated in FIG. 9.

The kinematic model is illustrated in FIGS. 8A, 8B and 8C. It isinitialised 133 with an approximate surface of the prostate in thereference image 205 and a rotation point which uses an approximation ofthe rotational constraints of the probe in the rectum 206. It is alsonecessary to know the position of the ultrasonographic head with respectto the image it produces as represented for example by the centre 202thereof, the orientation of the probe, still with respect to the imagealso called the “probe axis” 203 which can be represented by a vectorpointed towards the handle of the probe. With such information, it ispossible to estimate the position of the rectum with respect to theprostate and thus the region on the surface of the prostate which can bereached by the head of the probe. All the positions of the probe forwhich the head is in this region and for which the axis of the probegoes through the stationary rotation point is a correct approximation ofall the positions of the probe which are physically possible during thepositioning of the needle during a biopsy of the prostate. Theapproximation can be refined by modelising pressure fluctuations on theprostate by the clinician and varying the distance of the head to thesurface by a few millimetres. Eventually, it should be made discrete asuniformly as possible for the whole position herabove. As an example,the method can be concretely implemented with an approximate prostaticsurface biopsy 205 defined form a parallelepiped positioned by theclinician about the prostate visible in the reference image 201. Theregion which can be reached by the probe in the rectum is estimated fromthe point of intersection 208 of the line between the head of the probe202 and the centre of the surface 207 with the surface passing through apolar representation of the ellipsoid 210 parameterised with alpha andbeta angles 210 so that the point of intersection coincides with therepresentation for alpha and beta equal to zero. When limiting theabsolute values of alpha and beta, a region is defined which shows anapproximation of the part of the surface which can be reached by thehead of the probe. All the positions for the probe for which the head ison the surface and the axis goes through the rotation point 206 can besampled by following discretely alpha and beta parameters, each couplegiving a contact point 210 and a third angle gamma 211 which is a modelfor the rotations of the probe about the axis 203 thereof.

FIG. 9 illustrates a method for estimating the transformation of thetracking image to the reference image 125 implemented during theacquisitions of biopsies 104. Starting from the estimation of thesampling path in the first image of the list, this method makes itpossible to project the estimated path in the reference image. First, astatistic measure of the similarity is calculated between each image ofthe list of transformations and the tracking image 141. In anadvantageous manner, the method is operated with a measure of thesimilarity of the “Pearson correlation” type, “standardised mutualinformation”, “square distances sum” or “correlation ratio” type. Evenmore advantageously, it is possible to combine these or to combine theresults of the application thereof on several aspects of the image suchas the derivative or laplacian thereof. A list is then created 142, saidlist containing M transformations corresponding to the M bestmeasurements of step 141. A correct robustness of the system is obtainedwith M=5. If the matching is the first matching of a tracking image ofthe reference image, the method goes through step 144. If the matchingis not the first matching of a tracking image with the reference imageand the estimated transformation upon the last matching is added to thelist of M transformations 143 before going to the step 144. And for eachtransformation of the list, a local optimisation algorithm of thestatistical measure of the similarity from such information isimplemented 144. The object of the local optimisation 144 is to find thetransformation which optimises the similarity in the neighbourhood ofthe initial transformation using a conventional local optimisationalgorithm such as the Powell-Brent algorithm. Then, the best resultobtained from the step 144 is refined with a high quality localoptimisation algorithm 145. During such step, the same calculation asthe one used during the step 144 is applied, but this time withparameters making it possible to obtain a finer accuracy for a longercalculation time. Then, the final transformation giving the best resultfor the statistical similarity and refined according to said highquality algorithm is recorded 146.

The present invention gives the practitioner a better possibility oftreatment of cancer and potentially a quicker diagnostic and a morefocused therapy. In addition, the medical and surgical treatments aswell as convalescences can thus be shortened. The system also has aninterest in the learning of the gesture. A young practitioner needs onlybe shown that the puncture was not carried out where it should have beenand the training curve is accelerated.

As the endorectal prostate ultrasonography being is used for a certainnumber of therapeutic gestures often transperinal gestures(curietherapy, photodynamotherapy, cryotherapy), the present inventioncan be applied to therapeutic time. Then, the interest lies in that itgives the searcher or radiotherapist location information on therapeuticneedles when and as they are inserted while complying with a prioroperational planning. Then, when coupled with the integration ofanatomic (regionalisation of the gland) or statistic (probable zones ofpresence of cancer) information or additional mode images (RIM, Doppler,elastrography, contrast image, CT, PET, fluorescence, etc) or resultsfrom previous operations on the same patient, the system can superimposesuch new information with the reference ultrasonographic volume thusimproving the planning and the guiding of the gesture.

The implementation of the imaging method can advantageously be assistedby software guiding the practitioner. Such software guides thepractitioner in the succession of operations to be carried out in alinear way. Such software will first control the displaying ofinformation relating to the preliminary sequence of acquisition of thereference image. It controls the means for entering the patient'sinformation as well as, if need be, information relating to operationsconditions (date, name of the operator, pre-operational information suchas PSA or prostate volume, place of operation, etc.)

When all the compulsory information is recorded, the software controlsthe functionality relating to the acquisition of ultrasonographic imagesintended for the calculation of the reference image. When the quality ofthe reference image is validated by the operator or by an automaticprocessing, the software controls the following sequence correspondingto the sampling of biopsies. During this sequence, the software canrecord the ultrasonographic image acquired upon the triggering of a newsampling and visualise in real time a grouped image showing asuperimposed reference image and path for the new sampling after thestandardisation transformation.

When all biopsies have been carried out, the user controls thepreparation of the report and the archiving of data. The processing oftransformation of the acquired images to enable a superimposition on thereference image can be a transformation in the Cartesian space with theprostate being then assimilated to a solid object being subjected to nodeformation during the sampling steps.

It is possible to improve the treatment with a non-linear transformationconsidering the deformation of the prostate between the condition atrest and the condition of prostate submitted to a local pressure by theultrasonographic probe head as well as the action of the samplingneedle. This system consists in recalculating an intermediate image ofthe prostate upon the sampling when minimising discrepancies between onearea or identification points of the reference image and an area in theacquired image to match at its best a partial area to determine theidentification points. This intermediate image corresponds to a changein the identification of the acquired image for optimising thesuperimposition with the reference image.

Then a second processing consists in deforming the acquired and thusrepositioned image so as to match areas reference points of the acquiredimage with the reference image. The second transformation makes itpossible to improve the quality of the superimposition and thus of thefinal representation of the superimposition of the biopsy paths and thereference image. In order to improve again the quality of such asuperimposition, an advantageous solution consists in providing arecalculated acquired image validation step. Such validation can becarried out manually by the operator thus checking if the recalculatedimage is superimposed while it is visualised in a pertinent way on thereference image. Such verification is carried out with athree-dimensional visualisation, making it possible for the operator toexplore in space the superimposition of images and carry outverifications under various orientations.

Such verification can be automatic using an evaluation processing of thediscrepancies between the reference image and the recalculated imageusing the calculation of a measure of the similarity for automaticallyvalidating when the result of such measurement is lower than itsthreshold value. The measure of the similarity is estimated for eachstep during the phase convergence of the resetting method. Themeasurement function calculates, according to an exemplaryimplementation, the discrepancies between the canonical structuresidentified in the reference image and the acquired image for deliveringat the end of the path an evaluation of the final discrepancies and thusthe quality of the superimposition.

Another variant consists in integrating other previously or subsequentlyacquired images to superimpose these with the reference image and thebiopsies path. Such other images are for example an MRI image of theprostate, an image from the anatomic model or a model from the statisticdistribution of the tumoral areas or a series of images acquired on thesame patient on different dates.

1. A prostatic imaging method comprising recording and processing imagesacquired by an ultrasonographic head of a rectal probe equipped with anactive puncture guide, processing at least a part of the images acquiredby the probe for calculating transformations to a “reference image”repository relative to the initial position of a prostate, with at leasta part of the images acquired during successive punctures including alocation of various positions of a needle being recorded with a view tovisualising representations thereof on a single image including at leasta part of the prostate.
 2. An imaging method according to the precedingclaim, wherein the position of the sampling needle is visualised in the“reference image” repository or “tracking image” repository after thepuncture, superimposed on an image of at least a part of the prostateshowing the various positions of prior samplings.
 3. An imaging methodaccording to claim 1, wherein the position of the sampling needle isvisualised in real time in the “reference image” repository or “trackingimage” repository, being superimposed on an image of at least a part ofthe prostate showing the various
 4. An imaging method according to claim1, further comprising tumoral distribution is visualised in the“reference image” repository after merging of a spatial distribution ofthe marked punctures with results from anatomopathologic analysis.
 5. Animaging method according to claim 1, further comprising resetting a newprostatic image marked upon each new sampling.
 6. An imaging systemaccording to claim 1, further comprising a refreshing frequency of theimages acquired by the ultrasonographic probe being at least 3 imagesper second.
 7. An imaging method according to claim 1, furthercomprising using the ultrasonographic probe to give a three-dimensionalimage.
 8. An imaging method according to claim 1, further comprisingusing the ultrasonographic probe to give a “2.5-dimensional” type image.9. An imaging method according to claim 1, further comprisingchronological marking with a serial number implementing means for theunivocal labelling of each sampling area.
 10. An imaging methodaccording to claim 9, wherein the univocal labelling means are manuallygenerated with the needle being in position.
 11. An imaging methodaccording to claim 9, wherein the univocal labelling means are generatedby an automatic triggering of the acquisition of data through thecapture of a sound, light, tactile or magnetic signal at the exactmoment of biopsy sampling.
 12. An imaging method according to claim 1,wherein the step of processing the acquired images further implements akinematic model derived from anatomic constraints specific to atransrectal puncture of the prostate making it possible to identifyprobable positions of the probe during an operation.
 13. An imagingsystem according to claim 1, wherein the step of processing the acquiredimages further implements the process of pre-calculating the probablepositions of the probe during a biopsy and the images corresponding tothe positions of the probe pre-calculated from the reference image. 14.An imaging method according to claim 1, wherein the step of processingthe acquired images further implements an image resetting algorithmbased on the local optimisation of a measure of the similarity.
 15. Animaging method according to claim 1, further comprising using softwarefor successively controlling the entering of a patient's information, adisplay of the information relative to a preliminary sequence ofacquisition of the reference image, functionalities relating to theacquisition of the ultrasonographic images intended for the calculationof the reference image and when the quality of the reference image isvalidated by the operator or by an automatic processing, biopsiessampling sequence.
 16. An imaging method according to claim 1, whereinthe processing of the images consists of a non-linear transformation,taking into account a deformation of the prostate between a condition atrest and a condition of the prostate submitted to pressure.
 17. Animaging method according to claim 1, further comprising validatingrecalculated acquired image.
 18. An imaging method according to thepreceding claim, wherein the checking is automatised by a processing forevaluating discrepancies between the reference image and therecalculated image.
 19. An imaging method according to the precedingclaim, wherein the checking is automatised by a processing forevaluating the discrepancies between canonical structures registered inthe reference image and the acquired image, so as to finally issue anestimation of the final discrepancies.
 20. An imaging method accordingto claim 1, further comprising integrating other images previously orsubsequently acquired to superimpose these on the reference image andbiopsy paths.
 21. A prostatic imaging system comprising a rectal probeand a calculator, with the probe including an ultrasonographic head fortaking an image of a puncture area done with a needle actuated by anoperator, with the calculator recording and processing the imagesacquired by the ultrasonographic head, the calculator also recording andprocessing images required by the probe in order to calculatetransformations to a “reference image” repository relating to an initialposition of a prostate, with at least a part of the images acquiredduring successive punctures including a location of various positions ofthe needle being recorded with a view to visualising representationsthereof on a unique image including at least a part of the prostate. 22.A prostatic imaging system according to the preceding claim, furthercomprising a receptacle for collecting samples of tissues with anidentifier correlated with a marking of a corresponding sampling area ona single image of the marked prostate.
 23. A prostatic imaging systemaccording to claim 21, wherein the rectal probe is a manually activatedprobe without any robotised positioning.
 24. A prostatic imaging systemaccording to claim 21, wherein the rectal probe is a manually activatedprobe moved by an optical or magnetic locator.
 25. A prostatic imagingsystem according to claim 21, wherein the rectal probe is a probepositioned by a robot.
 26. A computer medium including recording of acalculator controlling program for the implementation of prostaticimaging, the computer medium comprising programming instructionsrecording and processing images acquired by an ultrasonoqraphic head ofa rectal probe equipped with an active puncture guide, processing atleast a part of the images acquired by the probe for calculatingtransformations to a “reference image” repository relative to theinitial position of a prostate, with at least a part of the imagesacquired during successive punctures including a location of variouspositions of a needle being recorded with a view to visualisingrepresentations thereof on a single image including at least a part ofthe prostate.